Without this million year old programming language, WordPress would most likely be a very different beast. It’s good fortune that both offer levels of backwards compatibility that are not often encountered in open source. From the WordPress mothership, Juliette Reinders Folmer: “In short, I’m proposing a fixed schedule in which every PHP version is supported for five years. Additionally each WordPress release will receive security updates for four years. In effect, this means that users, at a stretch, would be able to run on one specific PHP version for nine years.” I love having a transparent view into the versioning. I think nine years it crazy. It ultimately places an undue burden on hosting companies to police very old sites. Yes that’s part of the joy of running a host but ultimately gives WordPress a black-eye when you get reports of 100,000+ sites hacked. I hope this timeline gets much smaller.